The present invention relates to an electronic valve control for controlling the sloughing strokes in wet sloughing machines for coal and other minerals. The control has a stroke frequency generator which supplies recurrent signal codes to inlet and outlet sloughing stroke generators which are connected in parallel, with power amplifiers connected after the stroke generators to produce command pulses for inlet and outlet valves of the sloughing machine.
A method and apparatus for the processing of mineral mixtures, in particular unwashed coal, on an air-controlled wet sloughing machine is known for example from U.S. Pat. No. 4,019,981. In this reference a separating liquid is moved up and down periodically through the openings of the sloughing material support with the aid of control waves arranged in air and/or separating liquid feed lines. The pulsing movement of the separating liquid is effected by means of an electronic valve pulse control of compressed air supplied to the sloughing machine and/or by means of the separating liquid quantity supplied.
This known electronic valve pulse control, however, is not suitable for a valve control in sloughing machines which have one valve per sloughing chamber for the control of additive strokes and one valve for the control of the air outlet (German Pat. No. 26 54 593).